Conventionally, a technique of using X-ray diffraction is established, as a technique of measuring crystal lattice strain. As the technique of using X-ray diffraction, there is known a method of measuring crystal strain which utilizes a fact that a width of a diffraction line of X-ray diffraction obtained by irradiating X-ray to a semiconductor crystal as a sample broadens due to crystal strain, a method of obtaining a map of whole sample by irradiating X-ray to the sample and recording Bragg reflected ray from the sample, and other methods.
Also, there is known the micro Raman method, as a technique of measuring strain of microscopic portion of a crystal. As an example, Japanese patent laid-open publication No. 3-18744 discloses a method of measuring strain of a microscopic portion of a crystal using a laser Raman spectroscopy method. In this measuring method using the laser Raman spectroscopy method, a slit is formed at a thin film formed on a semiconductor substrate and thereby a portion of the semiconductor substrate is exposed. A laser light is then irradiated on the exposed surface of the semiconductor substrate, and crystal strain is measured from the spectroscopy spectrum of a reflected light thereof.
As another method of measuring strain of a microscopic portion of a crystal, there is also known a method using convergence-beam electron diffraction.
However, as semiconductor elements formed using a semiconductor crystal are highly integrated and size of each element becomes small, strain of crystal resulting from a stress exerted on a microscopic region within a semiconductor crystal becomes a problem. In the technique using X-ray diffraction, it is difficult to narrow down a spot of irradiated X-ray into a size equal to or smaller than several micrometers and, therefore, it was substantially impossible to measure the above-mentioned crystal strain resulting from a stress exerted on a microscopic region within a semiconductor crystal.
In the technique using the micro Raman method, it is possible to obtain a spatial resolution higher than that of the technique using X-ray diffraction. However, even in this technique, it was impossible to obtain a resolution sufficient to measure the above-mentioned crystal strain resulting from a stress exerted on a microscopic region within a semiconductor crystal.
Also, in the method using convergence-beam electron diffraction, it is possible to narrow down a diameter of an electron beam to, for example, 1 nm and thereby to measure strain of a microscopic portion of a crystal. However, when a distribution of crystal lattice strain throughout a sample is to be inspected, it is necessary to measure electron diffraction patterns over thousands of portions, and, therefore, enormous labor and time are required.